Metalurgi v37 640

Keywords: Magnesium ion separation, lithium ion separation, sodium silicate residue, seawater
 
 
1.
 
I
NTRODUCTION
 
Seawater in unlimited quantities is one of the 
future natural resource potentials. The volume of 
seawater in the hemisphere is estimated to be
1.3 x 10
18
tons, with a mineral content of 3.3%. 
Thus, the amount of minerals found in seawater 
around the world is estimated to be 3 x 10
16
tons 
[1]. According to data from the 2015 USGS 
Mineral Commodity Summaries, the following 
cations are eligible for development from 
seawater mineral resources: Na, Ca, Mg, K, Li, 
Sr, Br, B, and U [1]. Based on the analysis of 
samples from various seawater regions around 
the world, the lithium potential is estimated to be 
230 billion tons. While the world's known lithium 
reserves on land total only 14 million tons [2], 
When lithium reserves are compared, the ocean 
has 16,429 more lithium reserves than the land.
To ensure the availability of lithium raw 
materials, lithium extraction process technology 
must be developed while considering the 
potential of lithium from seawater resources. The 
adsorption method is commonly used in the 
research and development of lithium raw 
materials from marine natural resources. In 
contrast, lithium research and development on 
land typically employs the precipitation method 
for brine water and an alkaline digester for rocks 
[3]. One of the seawater lithium extraction 
studies 
using 
the 
adsorption 
method 
is 
manganese dioxide-based adsorbs. Research with 

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Metalurgi, V. 37.1.2022, P-ISSN 0126-3188, E-ISSN 2443-3926/ 21-30
manganese 
adsorption 
materials 
includes: 
adsorbing with sieve MnO
2
.0,5 H
2
O [4], with a 
mixture of lithium manganese dioxide and 
chitosan granules [5] and using λ -MnO
2
material 
in the form of hexagonal crystals [6]. The results 
of the three experiments showed that the 
adsorption capacity for the combination of MnO
2
with chitosan was 54.65 mg/g Li+ ions [5], the λ 
-MnO
2
hexagonal crystalline material was 24.7 
mg/g Li+ ions [6]. The sieve MnO
2
ion material, 
5 H
2
O is 10.05 mg/g Li+ ion [4]. In addition to 
the adsorption process, a continuous electrical 
pumping membrane process was developed with 
the results of increasing the lithium concentration 
from 0.1-0.2 ppm to 9013.43 ppm [7]. The 
electrolysis 
process 
using 
the 
Pulsed 
Electrochemical Intercalation method obtained 
lithium ion selectivity results of 1.8 x 104 [8], the 
process two-stage precipitation using NaOH, 
Na
2
CO
3
, and HCl with the product yield of 
Li
2
CO
3
content above 99% [9] and the separation 
process using metal aluminum foil [10]. 
Indonesia, a maritime country in the form of an 
archipelago, has the second longest beach in the 
world [11]. Therefore, mastery of seawater 
treatment technology into useful products must 
be done. Currently, the use of mineral resources 
from seawater in Indonesia is only in salt 
production. The total salt production in Indonesia 
from 44 regions in Indonesia was 2,915,461.17 
tons in 2016 [11]. Until now, there has been no 
use of seawater in Indonesia to produce lithium 
carbonate products. Constraints faced in the 
process of extracting lithium from seawater 
resources are the very high ratio of lithium to 
magnesium (ratio Mg/li) and low levels of 
lithium from seawater. For example, the lithium 
content of seawater on the Lamongan beach is 
0.17 ppm [12]. Based on the theory, with a low 
lithium content of about 0.18 ppm and an Mg/li 
ratio above 7000, it is challenging to be 
economically processed into lithium carbonate 
products [13]. 
In this research, the process of separating 
lithium ions and magnesium ions from seawater 
will be carried out using the sodium silicate 
precipitation process. In previous experiments 
with bittern as raw material from salt pond waste, 
the results obtained were only able to take up 
about 20% lithium ions, and the Mg/Li ratio was 
1033 [12]. The precipitation process is one of the 
most straightforward and most practical lithium 
and magnesium ion separation processes [14]. In 
several methods, separating lithium ions and 
magnesium ions in brine water with the 
precipitation process showed promising results. 
The 
separation 
process 
for 
lithium 
and 
magnesium ions includes the precipitation 
process with the following materials: aluminum 
metal powder and sodium sulfate [15], oxalic 
acid and sodium carbonate with brine water 
Bledug Kuwu as raw material [16], ammonium 
phosphate for lithium anolyte concentrate as raw 
material [17], and the precipitation process with 
sodium metasilicate as precipitating agent [18]. 
The separation of magnesium ions and lithium 
ions will do to obtain a filtrate containing only 
lithium ions and no magnesium ions. This filtrate 
will be use as a raw material in the production of 
lithium carbonate. Lithium carbonate is a key 
ingredient in the production of lithium batteries.